Multidimensional and three-dimensional (“3D”) presentations of information present specific challenges not found in two-dimensional (“2D”) presentations. For example, in 3D presentations certain elements may be occluded by the presence of other elements in the presentation. Traditional approaches to dealing with occlusion avoidance in 3D presentations include techniques such as cutting planes, viewer navigation, filtering of information, and transparency. While these methods provide clearer visual access to elements of interest, they remove much of the contextual information from a presentation.
In 2D presentations all information is restricted to a plane perpendicular to a view point. The addition of the third spatial variable (or z component) in 3D presentations allows objects to be interposed or positioned between the viewpoint and other objects in a scene, thus partially or completely hiding them from view. The preservation of spatial relationships and presentation of relationships to the occluding objects is important in constructing a physically plausible scene, or in other words, for maintaining the detail of the scene in the context in which it exists. For example, in volumetric rendering of 3D data it is often the case that the near-continuous nature of the data makes occlusion of interior features of the data inevitable. This phenomenon is important in supporting the perception of the scene as a 3D presentation, but a user may very well wish to examine these hidden interior features and regions.
Solutions are available that provide visual access (i.e., clear lines of sight) to previously occluded elements. Several of these solutions are described by Cowperthwaite (Cowperthwaite, David J., Occlusion Resolution Operators for Three-Dimensional Detail-In-Context (Burnaby, British Columbia: Simon Fraser University, 2000), which is incorporated herein by reference. Cutting planes may be used to remove information from a scene. Increasing transparency (or reducing the opacity) of objects allows more distant objects to be seen through those more proximal to the viewer. Navigation of the viewer, whether egocentric (moving the viewer within the data space) or exocentric (moving or re-orientation of the data space) may lead to a configuration where occlusion is resolved. Finally, information filtering may be used to reduce the density of data in a representation. These are all common methods of occlusion resolution and all operate by reducing the amount (or visibility) of contextual information in the final presentation. Similar methods such as panning zooming and filtering have also been traditionally applied to dealing with large or congested displays of information in 2D. Thus, the removal of information from a presentation has been one approach to dealing with occlusion in large information spaces.
Another approach has been the development of “detail-in-context” presentation algorithms. The field of detail-in-context viewing is concerned with the generation of classes of information presentations where areas or items defined as focal regions or regions-of-interest are presented with an increased level of detail, without the removal of contextual information from the original presentation. For example, regions of greatest interest may be displayed at an enlarged size, providing more visual detail, while the scale of the surrounding context may be adjusted to provide the space for the magnification of the region-of-interest.
Thus, in 3D computer graphics and 3D information presentations generally, occlusion of objects of interest by other objects in the viewer's line of sight is a common problem. U.S. Pat. No. 6,798,412, which is incorporated herein by reference, describes methods of occlusion reduction based on displacements orthogonal to the line of sight and based on a variety of distance metrics and shaping functions. What are now needed are additional methods and improvements to methods for occlusion reduction and magnification.
A need therefore exists for an improved method and system for reducing occlusion and providing magnification in multidimensional data presentations. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.